1. Field of the Invention
The present invention generally relates to sterilization processes, and more particularly, to the techniques for monitoring the efficacy of a container or a pouch system.
2. Description of the Related Art
A sterilization process generally involves in exposing the articles to be sterilized to a sterilizing medium that can kill bacterial microorganisms. Such processes are performed in sterilization chambers. The articles to be sterilized are often delivered to the sterilization chambers within a sterilization container in which the articles are both sterilized and subsequently stored in their sterilized state. In some instances, articles are merely disinfected, but are often nevertheless delivered within a container.
The containers are generally permeable to a sterilizing medium so that the sterilizing medium may enter the container during the sterilization process. A sterilizing medium may be a sterilant gas or vapor (e.g., hydrogen peroxide vapor) released by a sterilant source which is placed into or delivered into the sterilization container. As used hereinafter, the terms xe2x80x9cgasxe2x80x9d and xe2x80x9cvaporxe2x80x9d are used interchangeably. Such gas permeable containers may, for example, include pouches made of gas permeable materials or rigid trays wrapped with gas permeable wraps. In fact, a sterilization container may be configured as a sealable rigid container having ports to deliver a sterilant after the container has been sealed. In all above examples, however, the sterilization containers prevent the entry of the microorganisms into the container and thereby maintain the sterilized state of the articles therein.
In modern medical and dental practice, it is important to monitor the efficacy of the sterilization processes. That is, at the end of the sterilization cycle, it must be verified that all of the articles have been adequately exposed to the sterilizing medium and the existing microorganisms have been killed. Conventional sterilization processes commonly have two underlying monitoring devices that address such concerns, namely, biological indicators and chemical indicators. A biological indicator (BI) is a type of device having a source of microorganisms. In this context, the source of microorganisms refers to a predetermined concentration and type of microorganisms which are generally impregnated into coated onto a substrate, such as paper, fiberglass, or stainless steel. A biological indicator is used to monitor the sterilization process and determine whether the particular sterilant succeeded in killing or inactivating all the microorganisms in the load to be sterilized. In practice, the biological indicator is maintained in a package which is made of gas permeable materials. During the sterilization process, the biological indicators are conventionally placed outside the sterilization containers so that the biological indicator can be retrieved without compromising the sterility of the devices within the container. After exposure to the sterilization process, the source of microorganisms is placed in a sterile culture medium and incubated for a pre-determined period of time. Any surviving microorganisms or growth of microorganisms indicates the incompleteness of the sterilization process in the container. One example of such a BI is shown in the Smith, U.S. Pat. No. 5,552,320, issued Sep. 3, 1996, incorporated herein by reference. Alternatively, a source of enzymes which mimic the response of living organisms to the sterilization procedure in a measurable fashion may be substituted for living microorganisms. Examples of this type of BI are shown in the Matner, U.S. Pat. No. 5,073,488 issued Dec. 17, 1991 and the Burnham, U.S. Pat. No. 5,486,459, issued Jan. 23, 1996, each of which are incorporated herein by reference.
On the other hand, chemical indicators (CI) are devices that primarily indicates whether or not the sterilization process cycle is carried out properly to deliver the sterilant to the sterilization chamber. Thus, chemical indicators do not necessarily provide a true indication that sterility has been achieved. Chemical indicators contain specific chemical compositions which chemically reacts and change color or other configurations when exposed to the sterilizing medium. Additionally, chemical indicators may be designed to include and respond to a plurality of sterilization process parameters. For example, depending on the classification of the chemicals indicator, a chemical indicator can be designed to indicate or respond to certain sterilant concentrations, humidity, time, temperature, sterilant""s pH or pressure.
During conventional sterilization processes, biological and chemical indicators are typically placed outside the gas permeable sterilization containers in which the load of the articles to be sterilized are placed. Upon completion of the sterilization process, containers, which are in their sealed state and with a presumably sterilized load, are often stored for a period of time before the sterilized articles are needed. In such conventional processes, the actual state of the sterilization inside the container is determined by inspecting the indicators located outside the container to determine whether the sterilization has been achieved. However, in practice, this approach has serious drawbacks because these indicators cannot provide accurate information about the sterilization status of the articles in the container. Since the indicators only display the outside readings, there is no way of knowing whether sterilization has been achieved inside the container.
An alternative approach utilizes two chemical indicators to overcome the above given drawback. In this approach one of the chemical indicators is placed into the container adjacent to the load of articles. Unfortunately, the problem with this approach is that the actual state of the sterilization can only be determined by opening the container and inspecting the chemical indicator placed inside the container. However, this is also not practical and disturbs the sealed state of the container and the sterility of the devices therein. There also is a possibility that sterilization conditions were not achieved inside the container. Accordingly, throughout the storage period, the actual state of the sterilization process cannot be known.
Some container systems have a clear barrier through which a chemical indicator, but not a biological indicator, can be read. However, such chemical indicators cannot be removed without breaking the barrier. Moreover, in such a system, the chemical indicator is included within the load, so it is exposed to sterilant at the same time as the load. As a result, the chemical indicator may indicate a sterile result, even when portions of the load have not been exposed to sufficient sterilant to achieve sterility.
In view of the foregoing, there is a need for a new monitoring system for sterilization processes which is capable of indicating the state of the sterilization in an enclosed sterilization container while maintaining the sealed state of the sterilization container.
A system, according to the present invention, for monitoring a sterilization or disinfection process comprises a container defining a first space and a second space which are in fluid communication with each other. The first space is adapted to contain one or more articles to be sterilized or disinfected and the second space contains therein at least one indicator for indicating a parameter relevant to the sterilization or disinfection process. An antimicrobial source provides an antimicrobial agent to the first space. The second area is in fluid communication with the antimicrobial source only through the first space.
The antimicrobial source can comprise an aperture into the first space from outside of the container whereby antimicrobial fluids in an area around the container may diffuse into the first space through the aperture. Alternatively, the antimicrobial source can comprise a supply of antimicrobial fluid within the first space. Preferably, the antimicrobial fluid comprises hydrogen peroxide, and more preferably hydrogen peroxide vapor.
Preferably, the container is impermeable to microorganisms. A flow restriction can be provided between the first space and the second space. The second space may be detachable from the first space.
In one aspect of the invention, the container comprises a pouch.
The he indicator preferably comprises a biological indicator or a chemical indicator. When the container comprises a pouch, one convenient option is to print the chemical indicator on the pouch inside the second space.
In another aspect of the invention, the first space is divided into two or more subspaces connected in series between the source of antimicrobial fluid and the second space. One, more, or all of these subspaces, in addition to the second space can be made so as to be detachable from each other. A fan can be provided to assist flow through the container from the source of antimicrobial fluid to the second space.
A method, according to the present invention, for monitoring a disinfection or sterilization procedure comprises providing a container or pouch impermeable to microorganisms having a first space and a second space in fluid communication with each other. An article to be disinfected or sterilized is placed into the first area and an indicator is placed into the second area. An antimicrobial agent is provided in the first space and flowed to the second area only from the first area. A relevant function of the disinfection or sterilization procedure is read with the indicator.
The antimicrobial agent can be recirculated back to the first space from the second space.
When the container is a pouch the first space can be sealed from the second space after flowing the antimicrobial agent into the second space and then the indicator can be removed from the second space. The sealing can be accomplished by heat sealing a portion of the pouch between the first space and the second space.